Electrical Conductivity Boost: In Situ Polypyrrole Polymerization in Monolithically Integrated Surface-Supported Metal-Organic Framework Templates.

Recent progress in synthesizing and integrating surface-supported metal-organic frameworks (SURMOFs) has highlighted their potential in developing hybrid electronic devices with exceptional mechanical flexibility, film processability, and cost-effectiveness. However, the low electrical conductivity of SURMOFs has limited their use in devices. To address this, researchers have utilized the porosity of SURMOFs to enhance electrical conductivity by incorporating conductive materials. This study introduces a method to improve the electrical conductivity of HKUST-1 templates by in situ polymerization of conductive polypyrrole (PPy) chains within the SURMOF pores (named as PPy@HKUST-1). Nanomembrane-origami technology is employed for integration, allowing a rolled-up metallic nanomembrane to contact the HKUST-1 films without causing damage. After a 24 h loading period, the electrical conductivity at room temperature reaches approximately 5.10-6 S m-1 . The nanomembrane-based contact enables reliable electrical characterization even at low temperatures. Key parameters of PPy@HKUST-1 films, such as trap barrier height, dielectric constant, and tunneling barrier height, are determined using established conduction mechanisms. These findings represent a significant advancement in real-time control of SURMOF conductivity, opening pathways for innovative electronic-optoelectronic device development. This study demonstrates the potential of SURMOFs to revolutionize hybrid electronic devices by enhancing electrical conductivity through intelligent integration strategies.

Rapid and Versatile Biosensing of Liposome Encapsulation Efficiency Using Electrical Conductivity Sensor.

Liposomes are prominent nanosystems for drug delivery, with potential extending beyond isolated drugs. Ethanol-aqueous plant extracts can be encapsulated within liposomes to protect bioactive compounds (secondary metabolites) from rapid oxidation and enable sustained release. Determining which compound classes are present in each extract and the encapsulation efficiency (EE) of these extracts in liposomes is crucial for nanocarrier functionality. This involves assessing the ratio of bioactive substances within liposomes to the total content. However, quantifying EE for non-isolated compounds poses challenges due to the need for advanced analytical equipment and biosensing approaches. This study introduces an innovative method for EE quantification, using a conductivity electrode (k = 0.842/cm) to establish an EE biosensing technology. By correlating dynamic light scattering (DLS), zeta potential (ZP), and electrical conductivity (Cnd) data with the conductivity meter's calibration curve, a robust relationship between the free extract concentration and Cnd (r2 ≥ 0.950) was established. Lavender-loaded liposomes demonstrated an EE of 56.33%, while wormwood and oregano formulations exhibited high EEs of 94.33% and 91.70%, respectively. In contrast, sage-loaded liposomes exhibited an inadequate EE, encapsulating only approximately 0.57% of the extract. The straightforward quantification of the free extract within liposome formulations, compared to more complex approaches, could facilitate EE determination and support future characterizations.

Electrical Conductivity and In Situ SAXS Probing of Block Copolymer Nanocomposites Under Mechanical Stretching.

Elastomers based on block copolymers can self-organize into ordered nanoscale structures, making them attractive for use as flexible conductive nanocomposites. Understanding how ordered structures impact electrical properties is essential for practical applications. This study investigated the morphological evolution of flexible conductive elastomers based on polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) block copolymers with aligned single- or multi-wall carbon nanotubes (SWCNTs or MWCNTs) and their electrical conductivity under large deformations. Oriented nanocomposites were obtained through injection molding and characterized using two different setups: tensile testing monitored by in situ small-angle X-ray scattering (SAXS) and tensile testing with simultaneous electrical conductivity measurements. Our findings demonstrate that structural orientation significantly influences electrical conductivity, with higher conductivity in the longitudinal direction due to the preferred orientation of carbon nanotubes. Tensile testing demonstrated that carbon nanotubes accelerate the process of realignment of the ordered structure. As a consequence, higher deformations reduced the conductivity of samples with longitudinal alignment due to the disruption of percolation contacts between nanotubes, while in samples with a transverse alignment the process promoted the formation of a new conductive network, increasing electrical conductivity.

Characterization of the Key Compounds of Bell Pepper by Spectrophotometry and Gas Chromatography on the Effects of Induced Stress on the Concentration of Secondary Metabolite.

Sweet peppers are consumed worldwide, and traditional uses have sparked interest in their applications as dietary antioxidants, which can be enhanced in plants using elicitors. These are endowed with phytochemicals with potential health benefits such as antioxidants, bioavailability, and bioaccessibility. The trend in metabolomics shows us chemical fingerprints linking metabolomics, innovative analytical form, and bioinformatics tools. The objective was to evaluate the impact of multiple stress interactions, elicitor concentrations, and electrical conductivity on the concentration of secondary metabolites to relate their response to metabolic pathways through the foliar application of a cocktail of said elicitors in pepper crops under greenhouse conditions. The extracts were analyzed by spectrophotometry and gas chromatography, and it was shown that the PCA analysis identified phenolic compounds and low molecular weight metabolites, confirming this as a metabolomic fingerprint in the hierarchical analysis. These compounds were also integrated by simultaneous gene and metabolite simulants to obtain effect information on different metabolic pathways. Showing changes in metabolite levels at T6 (36 mM H2O2 and 3.6 dS/m) and T7 (0.1 mM SA and 3.6 dS/m) but showing statistically significant changes at T5 (3.6 dS/m) and T8 (0.1 mM SA, 36 mM H2O2, and 3.6 dS/m) compared to T1 (32 dS/m) or control. Six pathways changed significantly (p < 0.05) in stress-induced treatments: aminoacyl t-RNA and valine-leucine-isoleucine biosynthesis, and alanine-aspartate-glutamate metabolism, glycoxylate-dicarboxylate cycle, arginine-proline, and citrate. This research provided a complete profile for the characterization of metabolomic fingerprint of bell pepper under multiple stress conditions.

Phytogenotoxicity of thymol and semisynthetic thymoxyacetic acid in pre/post emergence of model plants and weeds.

Herbicides are commonly used to control weed. However, some plants are resistant to such products. To identify less harmful herbicides, it is crucial to search for different mechanisms of action. Thymol is an easily acquired allelopathic compound, capable of producing its respective semisynthetic derivative, thymoxyacetic acid. The aim of this study was to determine the effects of thymol and thymoxyacetic acid molecules as bioherbicides in greenhouse at the concentration of 3 mmol L-1 in pre- and postemergence applications in five species: Amaranthus viridis L., Cucumis sativus L., Lactuca sativa L., Eleusine indica L., and Sorghum bicolor L. The initial seedling development and DNA changes were analyzed. These molecules were contrasting with the solvent, in the negative control, and with the glyphosate, in the positive control, promoting phytogenotoxic activities. The toxic effect of thymoxyacetic acid was more effective in preemergence and thymol's in postemergence. We also observed a reduction in the germination speed index and root growth with a negative correlation to the increase in potassium leaching. Damage to the root and shoot of the seedlings was verified at the DNA level, and the phytotoxicity of the plants treated with the herbicide glyphosate was similar to the plants treated with the natural molecules tested. The bioherbicidal effect of thymol and thymoxyacetic acid exacerbates the reduction of the environmental impact caused by the disordered and increased use of residual pesticides.

Simulations of surface charge density changes during the untreated solid tumour growth.

Understanding untreated tumour growth kinetics and its intrinsic behaviour is interesting and intriguing. The aim of this study is to propose an approximate analytical expression that allows us to simulate changes in surface charge density at the cancer-surrounding healthy tissue interface during the untreated solid tumour growth. For this, the Gompertz and Poisson equations are used. Simulations reveal that the unperturbed solid tumour growth is closely related to changes in the surface charge density over time between the tumour and the surrounding healthy tissue. Furthermore, the unperturbed solid tumour growth is governed by temporal changes in this surface charge density. It is concluded that results corroborate the correspondence between the electrical and physiological parameters in the untreated cancer, which may have an essential role in its growth, progression, metastasis and protection against immune system attack and anti-cancer therapies. In addition, the knowledge of surface charge density changes at the cancer-surrounding healthy tissue interface may be relevant when redesigning the molecules in chemotherapy and immunotherapy taking into account their polarities. This can also be true in the design of completely novel therapies.

Determinación de viabilidad, vigor y banco de semillas de retamo espinoso (Ulex europaeus L.) en un Andisol de un ecosistema de Páramo

El retamo espinoso (Ulex europaeus L.) es una planta introducida invasora de rápido crecimiento y diseminación, con producción de semillas, que permanecen latentes en los primeros 5 cm de profundidad del suelo; esta planta altera espacios ecológicos nativos, áreas de producción agropecuaria y su control y erradicación no es exitosa. Conocer ciertas características de las semillas del retamo facilitará su control. Así, el objetivo de este trabajo, fue determinar el vigor, la viabilidad y el banco de semillas de retamo espinoso, en zonas del páramo de Sumapaz. Para las pruebas, se colectaron semillas en tres sitios: Delicias, Usabá y Laguna. La prueba de vigor, se llevó a cabo mediante conductividad eléctrica y la de viabilidad, por ensayo topográfico de tetrazolio; en cada prueba, se realizó cuatro repeticiones, cada una con 100 semillas; el diseño estadístico fue completamente al azar. Para el banco de semillas, se tomaron muestras de suelo, a profundidades 0-5, 5-10 y 10-20 cm y se dispusieron en bandejas de aluminio. La prueba de vigor mostró que, después de 6 horas de hidratación, la cantidad de iones lixiviados se estabilizó, con un valor de 38,51 µs.cm -1 g-1, a las diez horas, afirmando alto vigor de semillas. La prueba de viabilidad presentó un 98 % y el banco de semillas registró mayor cantidad en el horizonte de 10-20 cm, con 950 semillas.m2, en la Laguna. Este estudio demuestra que las semillas de retamo tienen altos valores de vigor, viabilidad y un abundante banco de semillas distribuidas a diferentes profundidades.

The gorse (Ulex europaeus L.) is an invasive introduced plant of rapid growth and spread, with seeds production that remain dormant in the first 5 cm of soil depth, this plant alters native ecological spaces, areas of agricultural production, and its control and eradication is not successful. Know certain characteristics of gorse seeds will facilitate its control. Thus, the purpose of this work was to determine the vigor, viability and seed bank of gorse in areas of the Sumapaz paramo. For the tests, seeds were collected in three sites: Delicias, Usabá and Laguna. The vigor test was carried out by means of electrical conductivity and the viability test by tetrazolium topographic assay, in each test four repetitions were carried out, each with 100 seeds, the statistical design was completely random. For the seed bank, soil samples were taken at depths of 0-5, 5-10 and 10-20 cm, and placed in aluminium trays. The vigor test showed that after 6 hours of hydration, the amount of leached ions stabilized with a value of 38.51 µs.cm -1 g-1 at ten hours, confirming high seed vigor. The viability test presented 98 % and the seed bank registered a greater quantity in the 10-20 cm horizon with 950 seeds.m2 in the Laguna. This study shows that gorse seeds have high values of vigor, viability, and an abundant seed bank distributed at different depths.

Tailoring Nylon 6/Acrylonitrile-Butadiene-Styrene Nanocomposites for Application against Electromagnetic Interference: Evaluation of the Mechanical, Thermal and Electrical Behavior, and the Electromagnetic Shielding Efficiency.

Nylon 6/acrylonitrile-butadiene-styrene nanocomposites were prepared by mixing in a molten state and injection molded for application in electromagnetic interference shielding and antistatic packaging. Multi-wall carbon nanotubes (MWCNT) and maleic anhydride-grafted ABS compatibilizer were incorporated to improve the electrical conductivity and mechanical performance. The nanocomposites were characterized by oscillatory rheology, Izod impact strength, tensile strength, thermogravimetry, current-voltage measurements, shielding against electromagnetic interference, and scanning electron microscopy. The rheological behavior evidenced a severe increase in complex viscosity and storage modulus, which suggests an electrical percolation phenomenon. Adding 1 to 5 phr MWCNT into the nanocomposites produced electrical conductivities between 1.22 × 10-6 S/cm and 6.61 × 10-5 S/cm. The results make them suitable for antistatic purposes. The nanocomposite with 5 phr MWCNT showed the highest electromagnetic shielding efficiency, with a peak of -10.5 dB at 9 GHz and a value around -8.2 dB between 11 and 12 GHz. This was possibly due to the higher electrical conductivity of the 5 phr MWCNT composition. In addition, the developed nanocomposites, regardless of MWCNT content, showed tenacious behavior at room temperature. The results reveal the possibility for tailoring the properties of insulating materials for application in electrical and electromagnetic shielding. Additionally, the good mechanical and thermal properties further widen the application range.

Salinity study of irrigation waters used in rice fields / Estudo da salinidade em águas de irrigação utilizadas na lavoura arrozeira

In Santa Catarina State, Brazil, rice is predominantly cultivated in irrigated systems, and irrigation water is generally collected directly from watercourses. Irrigated rice crops, which are sensitive to water salinity, form the basis of the economy of the Mampituba River Basin region, southern Brazil. This study aimed to assess salinity fluctuations in waters collected from the Mampituba River for irrigation of rice crops during the four seasons of the year. For salinity determination, water samples were collected from six sites along the river course, from the source to the mouth. Three subsamples were collected at each site, with a mean interval of 15 days between collections, beginning in May 2016 and ending in April 2017. Samples were evaluated for electrical conductivity (EC). Assessment of salinity damage was performed in seedlings of rice cultivars 'IRGA 417' and 'EPAGRI 106'. When seedlings reachedthe S2 stage, they were transplanted into flooded soil at different saline concentrations. EC values ranged from 224 to 20,120 µS cm−1over the experimental period, being higher at sites closer to the sea. The highest salinity values were recorded betweenNovember 2016 and January2017. It was possible to observe an inverse relationship between rainfall and water salinity. Salinity causes damage to rice plants, particularly seedlings. Symptoms include leaf tip chlorosis, leaf curling, and necrosis of old leaves. It is important forrice farmers to understand salt wedge fluctuations within their estuary as well as variations in salinity levels at different sites and times of the year.(AU)

No estado de Santa Catarina predomina na sua totalidade o cultivo de arroz irrigado e a água utilizada para a irrigação destas lavouras em sua maioria são retiradas diretamente de cursos de água. A região da Bacia Hidrográfica do Rio Mampituba tem sua economia baseada no cultivo do arroz irrigado, cujas plantas são sensíveis à salinidade. O presente trabalho objetivou determinar a flutuação de salinidade na água do Rio Mampituba (Sul do Brasil) utilizada para irrigação na lavoura arrozeira durante as quatro estações do ano. Para a determinação da salinidade foram realizadas coletas de água em seis locais no percurso do rio, desde sua nascente até a foz. Em cada local foram coletadas três subamostras de água com intervalo médio de 15 dias iniciado em maio de 2016 e finalizado em abril de 2017 e analisada a condutividade elétrica (CE). A caracterização do dano por salinidade em plântulas de arroz foi realizada nas cultivares IRGA 417 e EPAGRI 106. As plântulas foram transplantadas para solo inundado com diferentes concentrações salinas no estádio S2. A CE ao longo do período avaliado variou de 224 a 20.120 µS cm−1e foi maior nos pontos mais próximos ao mar. Os maiores valores de salinidade foram observados entre os meses de novembro de 2016 e janeirode 2017. Foi possível observar relação inversa entre a precipitação e a salinidade. A salinidade causa danos as plantas de arroz sendo os principais danos observados em plântulas. Estes danos foram clorose da ponta do limbo foliar, enrolamento foliar e necrose de folhas velhas. É importante que os orizicultores saibam como é a flutuação da cunha salina dentro do estuário, além de quais níveis incidem em cada local e em cada época do ano.(AU)

Productive characteristics of sunflower genotypes irrigated with different levels of saline water

Sunflower is suitable for family farmers from Northeast Brazil who are benefited by the production of grain and oil and is adequate for crop rotation and for honey production. The need for irrigation in this region leads to the realization of this study for evaluating the production components of four sunflower genotypes irrigated with different levels of water salinity. The study was carried out in the municipality of Remigio, Paraíba, Brazil, using a randomized block with split plots experimental design in a 5 x 4 factorial arrangement. Treatments consisted of five electrical conductivity levels of the irrigation water at 25 °C (L1 - 0.14 (reservoir water), L2 - 1.50, L3 - 2.50, L4 - 3.50, and L5 - 4.50 dS m- 1), and four sunflower genotypes (C1 - Embrapa 122-V2000, C2 - Olisun 03, C3 - AG 963, and C4 - Multissol) with three replicates. The irrigation water salinity levels tested did not influence the variables studied. Different values of the variables among sunflower genotypes were due to characteristics inherent to each genotype. Sunflower genotype Olisun 03 presented the highest oil content, while the lowest content was observed in Multissol.

Yield of prickly pear cactus irrigated with saline water in soils of the semi-arid region / Produtividade de palma forrageira irrigada com águas salinizadas em solos da região semiárida

Knowing the tolerance of plants grown in the Brazilian semi-arid region to salt stress is of paramount importance for the sustainability of regional agriculture. This study was developed to examine the growth and yield of prickly pear cactus 'Orelha de Elefante Mexicana' (Opuntia stricta Haw) irrigated with increasing water salinity levels (0.75, 3.0, 5.25 and 7.50 dS m-1 to 25 ºC) and grown on soils representative of the Brazilian semi-arid region (chromic Luvisol, Solonetz and Fluvisol). Total fresh weight decreased linearly, with a 21.42% reduction when we compare the average fresh weight per plant in the lowest and highest saline level treatments. The chromic Luvisol and Solonetz soils showed the best fresh weight and dry matter yields under the present experimental conditions.(AU)

Conhecer a tolerância das plantas cultivadas na região semiárida brasileira ao estresse salino, é de fundamental importância para a sustentabilidade da agricultura regional. Este trabalho objetivou avaliar o crescimento e produtividade de palma forrageira 'Orelha de Elefante Mexicana' (Opuntia stricta Haw), irrigada com níveis crescentes de salinidade da água (0,75; 3,0; 5,25; e 7,50 dS m-1 a 25 ºC) e cultivada sobre solos representativos da região semiárida brasileira (Luvissolo crômico, Planossolo nátrico e Neossolo flúvico). A massa verde total apresentou efeito linear decrescente havendo uma redução de 21,42 % ao comparar a massa verde média por planta do tratamento de menor nível com o tratamento de maior nível salino. Os solos Luvissolo crômico e Planossolo nátrico apresentaram as melhores produtividades de massa verde e massa seca nas condições deste experimento.(AU)

The Influence of Sonication Processing Conditions on Electrical and Mechanical Properties of Single and Hybrid Epoxy Nanocomposites Filled with Carbon Nanoparticles.

Graphene nanoplatelets (GNP) and carbon nanotubes (CNT) are used to enhance electrical and mechanical properties of epoxy-based nanocomposites. Despite the evidence of synergetic effects in the hybrid GNP-CNT-epoxy system, there is still a lack of studies that focus on the influence of different dispersion methods on the final properties of these ternary systems. In the present work, direct and indirect ultrasonication methods were used to prepare single- and hybrid-filled GNP-CNT-epoxy nanocomposites, varying the amplitude and time of sonication in order to investigate their effect on electrical and thermomechanical properties. Impedance spectroscopy was combined with rheology and electron microscopy to show that high-power direct sonication tends to degrade electrical conductivity in GNP-CNT-epoxy nanocomposites due to damage caused in the nanoparticles. CNT-filled samples were mostly benefitted by low-power direct sonication, achieving an electrical conductivity of 1.3 × 10-3 S·m-1 at 0.25 wt.% loading, while indirect sonication was not able to properly disperse the CNTs and led to a conductivity of 1.6 ± 1.3 × 10-5. Conversely, specimens filled with 2.5 wt. % of GNP and processed by indirect sonication displayed an electrical conductivity that is up to 4 orders of magnitude higher than when processed by direct sonication, achieving 5.6 × 10-7 S·m-1. The introduction of GNP flakes improved the dispersion state and conductivity in hybrid specimens processed by indirect sonication, but at the same time impaired these properties for high-power direct sonication. It is argued that this contradictory effect is caused by a selective localization of shorter CNTs onto GNPs due to strong π-π interactions when direct sonication is used. Dynamic mechanical analysis showed that the addition of nanofillers improved epoxy's storage modulus by up to 84%, but this property is mostly insensitive to the different processing parameters. Decrease in crosslinking degree and presence of residual solvent confirmed by Fourier-transform infrared spectroscopy, however, diminished the glass transition temperature of the nanocomposites by up to 40% when compared to the neat resin due to plasticization effects.

Mechanosynthesis and Thermoelectric Properties of Fe, Zn, and Cd-Doped P-Type Tetrahedrite: Cu12-xMxSb4S13.

This contribution deals with the mechanochemical synthesis, characterization, and thermoelectric properties of tetrahedrite-based materials, Cu12-xMxSb4S13 (M = Fe2+, Zn2+, Cd2+; x = 0, 1.5, 2). High-energy mechanical milling allows obtaining pristine and substituted tetrahedrites, after short milling under ambient conditions, of stoichiometric mixtures of the corresponding commercially available binary sulfides, i.e., Cu2S, CuS, Sb2S3, and MS (M = Fe2+, Zn2+, Cd2+). All the target materials but those containing Cd were obtained as single-phase products; some admixture of a hydrated cadmium sulfate was also identified by XRD as a by-product when synthesizing Cu10Cd2Sb4S13. The as-obtained products were thermally stable when firing in argon up to a temperature of 350-400 °C. Overall, the substitution of Cu(II) by Fe(II), Zn(II), or Cd(II) reduces tetrahedrites' thermal and electrical conductivities but increases the Seebeck coefficient. Unfortunately, the values of the thermoelectric figure of merit obtained in this study are in general lower than those found in the literature for similar samples obtained by other powder processing methods; slight compositional changes, undetected secondary phases, and/or deficient sintering might account for some of these discrepancies.

Enhancement of Electrical Conductivity of Aluminum-Based Nanocomposite Produced by Spark Plasma Sintering.

This article focuses on exploring how the electrical conductivity and densification properties of metallic samples made from aluminum (Al) powders reinforced with 0.5 wt % concentration of multi-walled carbon nanotubes (MWCNTs) and consolidated through spark plasma sintering (SPS) process are affected by the carbon nanotubes dispersion and the Al particles morphology. Experimental characterization tests performed by scanning electron microscopy (SEM) and by energy dispersive spectroscopy (EDS) show that the MWCNTs were uniformly ball-milled and dispersed in the Al surface particles, and undesirable phases were not observed in X-ray diffraction measurements. Furthermore, high densification parts and an improvement of about 40% in the electrical conductivity values were confirmed via experimental tests performed on the produced sintered samples. These results elucidate that modifying the powder morphology using the ball-milling technique to bond carbon nanotubes into the Al surface particles aids the ability to obtain highly dense parts with increasing electrical conductivity properties.

Spark Plasma Sintering of Aluminum-Based Powders Reinforced with Carbon Nanotubes: Investigation of Electrical Conductivity and Hardness Properties.

This paper focuses on reporting results obtained by the spark plasma sintering (SPS) consolidation and characterization of aluminum-based nanocomposites reinforced with concentrations of 0.5 wt%, 1 wt% and 2 wt% of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Experimental characterization performed by SEM shows uniform carbon nanotube (CNT) dispersion as well as carbon clusters located in the grain boundary of the Al matrix. The structural analysis and crystallite size calculation were performed by X-ray diffraction tests, detecting the characteristic CNT diffraction peak only for the composites reinforced with MWCNTs. Furthermore, a considerable increment in the crystallite size value for those Al samples reinforced and sintered with 1 wt% of CNTs was observed. Hardness tests show an improvement in the composite surface hardness of about 11% and 18% for those samples reinforced with 2 wt% of SWNCTs and MWCNTs, respectively. Conductivity measurements show that the Al samples reinforced with 2 wt% of MWCNTs and with 0.5 wt% SWCNTs reach the highest IACS values of 50% and 34%, respectively.

Growth of forage palm cultivars irrigated with saline waters / Crescimento de cultivares de palma forrageira irrigadas com águas salinas

Forage palm (Cactaceae) is considered an important resource in the semiarid region of Brazil. This study aimed to analyze the effect of different levels of salinity in irrigation water on the growth of three forage palm cultivars. The study was conducted at the Federal University of Campina Grande (7° 12' 52.6" S; 35° 54' 22.3" W) in 120 L pots open to the sky. The experiment was a complete randomized block, with four replications and a 4 × 3 factorial arrangement. The treatments consisted of four levels of salinity in irrigation water with electrical conductivity of 0.2, 2.0, 3.8, and 5.6 dS m–¹, and three forage palm cultivars: Miúda or Doce (Nopalea cochenillifera Salm Dyck), Orelha de Elefante (Opuntia stricta), and Baiana or IPA–Sertânia (Nopalea cochenillifera Salm Dyck). At 150 days after treatments, it was evaluated: length, width and perimeter of primary and secondary cladodes and total number of cladodes. Variance analysis was performed using an F-test (p < 0.05); significant effects were subjected to quadratic regression analysis for the quantitative variable, and the Tukey test (p < 0.05) for the qualitative variable. Salinity levels in irrigation water did not affect the growth variables. There was a significant difference in the growth of forage palm as a function of its cultivar. The Baiana cultivar showed the highest vegetative growth of length and perimeter of primary and secondary cladodes, while Miúda and Orelha de Elefante presented the greatest cladode numbers for plant and cladode widths, respectively.

A palma forrageira é considerada um importante recurso forrageiro no Semiárido brasileiro. Assim, objetivou-se avaliar o efeito de diferentes níveis de salinidade da água de irrigação no crescimento de três cultivares de palma forrageira. O estudo foi realizado na Universidade Federal de Campina Grande (7°12'52,56' S; 35°54'22,26" O) em vasos de 120 L dispostos a céu aberto. O delineamento experimental foi em blocos casualizados em esquema fatorial 4 × 3, com 4 repetições. Os tratamentos consistiram de 4 níveis de salinidade da água de irrigação com condutividades elétricas de: 0,2; 2,0; 3,8 e 5,6 dS m-¹; e três cultivares de palma forrageira: Miúda ou Doce (Nopalea cochenillifera Salm Dyck), Orelha de Elefante (Opuntia stricta), Baiana ou IPA Sertânia (Nopalea cochenillifera Salm Dyck). Aos 150 dias após o início dos tratamentos, avaliou-se: comprimento, largura e perímetro de cladódios primários e secundários e número de cladódios totais. As variáveis foram submetidas à análise de variância pelo teste F (p < 0,05) e quando houve efeito significativo foi realizada análise de regressão linear e quadrática para a variável quantitativa e o teste de Tukey (p < 0,05), para a variável qualitativa. Os níveis de salinidade da água de irrigação não exerceram influência sobre as variáveis de crescimento. Existe diferença significativa no crescimento da palma forrageira em função de sua cultivar. A cultivar Baiana apresenta crescimento vegetativo superior para comprimento e perímetro de cladódio primário e secundário, enquanto que as cultivares Miúda e Orelha de Elefante são superiores para número de cladódios por planta e largura de cladódio, respectivamente.

Growth of forage palm cultivars irrigated with saline waters / Crescimento de cultivares de palma forrageira irrigadas com águas salinas

Forage palm (Cactaceae) is considered an important resource in the semiarid region of Brazil. This study aimed to analyze the effect of different levels of salinity in irrigation water on the growth of three forage palm cultivars. The study was conducted at the Federal University of Campina Grande (7° 12' 52.6" S; 35° 54' 22.3" W) in 120 L pots open to the sky. The experiment was a complete randomized block, with four replications and a 4 × 3 factorial arrangement. The treatments consisted of four levels of salinity in irrigation water with electrical conductivity of 0.2, 2.0, 3.8, and 5.6 dS m–¹, and three forage palm cultivars: Miúda or Doce (Nopalea cochenillifera Salm Dyck), Orelha de Elefante (Opuntia stricta), and Baiana or IPA–Sertânia (Nopalea cochenillifera Salm Dyck). At 150 days after treatments, it was evaluated: length, width and perimeter of primary and secondary cladodes and total number of cladodes. Variance analysis was performed using an F-test (p < 0.05); significant effects were subjected to quadratic regression analysis for the quantitative variable, and the Tukey test (p < 0.05) for the qualitative variable. Salinity levels in irrigation water did not affect the growth variables. There was a significant difference in the growth of forage palm as a function of its cultivar. The Baiana cultivar showed the highest vegetative growth of length and perimeter of primary and secondary cladodes, while Miúda and Orelha de Elefante presented the greatest cladode numbers for plant and cladode widths, respectively.(AU)

A palma forrageira é considerada um importante recurso forrageiro no Semiárido brasileiro. Assim, objetivou-se avaliar o efeito de diferentes níveis de salinidade da água de irrigação no crescimento de três cultivares de palma forrageira. O estudo foi realizado na Universidade Federal de Campina Grande (7°12'52,56' S; 35°54'22,26" O) em vasos de 120 L dispostos a céu aberto. O delineamento experimental foi em blocos casualizados em esquema fatorial 4 × 3, com 4 repetições. Os tratamentos consistiram de 4 níveis de salinidade da água de irrigação com condutividades elétricas de: 0,2; 2,0; 3,8 e 5,6 dS m-¹; e três cultivares de palma forrageira: Miúda ou Doce (Nopalea cochenillifera Salm Dyck), Orelha de Elefante (Opuntia stricta), Baiana ou IPA Sertânia (Nopalea cochenillifera Salm Dyck). Aos 150 dias após o início dos tratamentos, avaliou-se: comprimento, largura e perímetro de cladódios primários e secundários e número de cladódios totais. As variáveis foram submetidas à análise de variância pelo teste F (p < 0,05) e quando houve efeito significativo foi realizada análise de regressão linear e quadrática para a variável quantitativa e o teste de Tukey (p < 0,05), para a variável qualitativa. Os níveis de salinidade da água de irrigação não exerceram influência sobre as variáveis de crescimento. Existe diferença significativa no crescimento da palma forrageira em função de sua cultivar. A cultivar Baiana apresenta crescimento vegetativo superior para comprimento e perímetro de cladódio primário e secundário, enquanto que as cultivares Miúda e Orelha de Elefante são superiores para número de cladódios por planta e largura de cladódio, respectivamente.(AU)

Physiological responses of watercress to brackish waters and different nutrient solution circulation times / Respostas fisiológicas de agrião com águas salobras e diferentes tempos de circulação da solução nutritiva

Water scarcity and the use of brackish water are the main challenges for agricultural development. In view of this, the present study proposes to examine physiological responses of the broadleaf-cress crop in an NFT hydroponics system according to the use of brackish water and nutrient solution circulation times. The treatments were distributed in a randomized block design with five water salinity levels (ECw: 0.6, 1.6, 2.6, 3.6 and 4.6 dS m-1) and two nutrient solution circulation times (T1 = 10 min and T2 = 15 min), totaling 10 treatments with four replicates, which resulted in 40 experimental plots. The following variables were analyzed: net photosynthetic rate, stomatal conductance, transpiration, leaf proline content, shoot moisture content, stem diameter and root length. The maximum observed photosynthetic rates were 20.9 mmol m-2 s-1 (T1) and 20.0 mmol m-2 s-1 (T2). Maximum stomatal conductance was 0.44 mol m-2 s-1, which decreased by 63.4% at the highest salinity level. The increasing ECw levels in both growing cycles evaluated reduced gas exchanges, stem diameter and root length. The nutrient solution circulation time of 15 min provided the most satisfactory results for the analyzed variables.(AU)

A escassez hídrica e o uso de água salobras são os principais desafios para o desenvolvimento agrícola. Diante disto o objetivo deste trabalho foi avaliar respostas fisiológicas da cultura do agrião d água de folhas larga em sistema hidropônico NFT em função do uso de águas salobras e tempos de circulação da solução nutritiva. Os tratamentos foram distribuídos em delineamento em blocos casualizados, com cinco níveis de salinidade da água (CEa: 0,6; 1,6; 2,6; 3,6 e 4,6 dS m-1) e dois tempos de circulação da solução nutritiva, (T1 =10 e T2=15 min), totalizando 10 tratamentos com 4 repetições, resultando em 40 parcelas experimentais. As variáveis analisadas foram: taxa de fotossíntese líquida, condutância estomática, transpiração, teor foliar de prolina, teor de umidade da parte aérea das plantas, diâmetro doc aule e comprimento das raízes. A máxima fotossíntese observada foi de 20,9 mmol m-2 s-1 (T1) e 20,0mmol m-2 s-1 (T2), para a condutância estomática foi 0,44 mol m-2s-1 provocando decréscimo 63,4%. O aumento dos níveis de CEa, em ambos os ciclos de cultivo avaliados, reduziram os valores de trocas gasosas, diâmetro do caule e comprimento da raiz. O tempo de 15 min promoveu os resultados mais satisfatórios para as variáveis analisadas.(AU)

Interpreting rheology and electrical conductivity: It all boils down to which particle size.

HYPOTHESIS: The electrical charges that develop on the surface of the ceramic particles upon contact with water, due to the interaction with ions in solution, result in a liquid-solid interface, which utterly modifies the properties of individual particles and the way they interact with each other to form a structure. This work explores a new approach to the relationships between structure and stability of suspensions. EXPERIMENTS: For this purpose, suspensions with a constant 0.35 volume fraction of α-alumina particles, neither spherical nor smooth, and controlled ionic strength (0-90 mM KCl) were prepared and characterized in terms of flow behaviour, electrical conductivity and particle's electrokinetic mobility. FINDINGS: Electrical conductivity (132 µS/cm < conductivity < 5730 µS/cm) and rheology measurements (10-2 Pa s < viscosity < 104 Pa s) were found to complement each other to produce a more accurate picture of the suspension's structure. Deviations of experimental data from well-accepted behavioural models were elucidated when the surface area equivalent particle size was used. With the electrical double layer thickness obtained from electrical conductivity measurements, this enabled the interpretation of the relationship between the suspension's viscosity and the particles electrical conductivity, which provides a criterion for the stability of concentrated colloidal suspensions.

Physiological responses of watercress to brackish waters and different nutrient solution circulation times / Respostas fisiológicas de agrião com águas salobras e diferentes tempos de circulação da solução nutritiva

Water scarcity and the use of brackish water are the main challenges for agricultural development. In view of this, the present study proposes to examine physiological responses of the broadleaf-cress crop in an NFT hydroponics system according to the use of brackish water and nutrient solution circulation times. The treatments were distributed in a randomized block design with five water salinity levels (ECw: 0.6, 1.6, 2.6, 3.6 and 4.6 dS m-1) and two nutrient solution circulation times (T1 = 10 min and T2 = 15 min), totaling 10 treatments with four replicates, which resulted in 40 experimental plots. The following variables were analyzed: net photosynthetic rate, stomatal conductance, transpiration, leaf proline content, shoot moisture content, stem diameter and root length. The maximum observed photosynthetic rates were 20.9 mmol m-2 s-1 (T1) and 20.0 mmol m-2 s-1 (T2). Maximum stomatal conductance was 0.44 mol m-2 s-1, which decreased by 63.4% at the highest salinity level. The increasing ECw levels in both growing cycles evaluated reduced gas exchanges, stem diameter and root length. The nutrient solution circulation time of 15 min provided the most satisfactory results for the analyzed variables.

A escassez hídrica e o uso de água salobras são os principais desafios para o desenvolvimento agrícola. Diante disto o objetivo deste trabalho foi avaliar respostas fisiológicas da cultura do agrião d’ água de folhas larga em sistema hidropônico NFT em função do uso de águas salobras e tempos de circulação da solução nutritiva. Os tratamentos foram distribuídos em delineamento em blocos casualizados, com cinco níveis de salinidade da água (CEa: 0,6; 1,6; 2,6; 3,6 e 4,6 dS m-1) e dois tempos de circulação da solução nutritiva, (T1 =10 e T2=15 min), totalizando 10 tratamentos com 4 repetições, resultando em 40 parcelas experimentais. As variáveis analisadas foram: taxa de fotossíntese líquida, condutância estomática, transpiração, teor foliar de prolina, teor de umidade da parte aérea das plantas, diâmetro doc aule e comprimento das raízes. A máxima fotossíntese observada foi de 20,9 mmol m-2 s-1 (T1) e 20,0mmol m-2 s-1 (T2), para a condutância estomática foi 0,44 mol m-2s-1 provocando decréscimo 63,4%. O aumento dos níveis de CEa, em ambos os ciclos de cultivo avaliados, reduziram os valores de trocas gasosas, diâmetro do caule e comprimento da raiz. O tempo de 15 min promoveu os resultados mais satisfatórios para as variáveis analisadas.